The first line looks good.
Here are some {{double braces}} in the text.
myvar = '' " this comment explains that '' is an empty string
:nnoremap <F3> :let @+='http://www.example.com/?item='.expand('<cword>')<CR>

Here is exactly the same text, using the insert space before each line technique:

Punctuation may be mistaken for wiki syntax, so the display may be incorrect.

Under some circumstances, if you select text from the spaced code block, you will find that each line has a trailing space (which is irritating if you want to paste the code into an example, and which can break some scripts).

On long code blocks, it is easier to insert <pre> before the block and </pre> after.